The invention is directed to a photonic cross-connect with reconfigurable add-drop functionality. Photonic, also called optical, cross-connects are based on the idea that a channel from a plurality of received WDM signals (wavelength division multiplex signals) can be redirected into any one of transmitted WDM signals. Most of the cross-connects avoid wavelength conversion, because it is cost effective at the expense of reduced signal quality, if optical-electrical conversion and 3R-regeneration are not used. Another restriction for the signal quality comes from the wavelength selective elements. These problems increase, if DWDM signals (dense wavelength division multiplex signals) are transmitted.
In future, high data-rates signals will be transported and routed through a network in frequency slots filled with a set of sub-channels at spectrally disjunctive optical frequencies. Such group of sub-channels is denoted as super-channel in the following. A super-channel is generated by combining e.g. 4 sub-channels by a pluggable module having several optical line side ports, or is generated directly by appropriate modules.
The optical cross-connect has to provide the functions to add and drop such sub-channels via tributary ports, and the function to direct the super-channels to the desired traffic directions via a direction switching unit.